Method of electrolytic reproduction



0a. 11, 1932; A. K. LAUKEL rmaon o1 ELECTROLYTIC REPRODUCTION Filed Aug.8. 1929 ATTORNEY The present invention pertains to the mak- PatentedOct. 11, 1932 ARTHUR K. LAUREL, OF DETROIT, MICHIGAN METHOD OFELECTROLYTIG'BEPRODUCTION I Application filed August. 8, 1929. SerialNo. 384,285.

Although various mean UNITED STATES PATENT orFrca s of metallizing a ingof foundry patterns and core boxes by electrodeposition and particularlto a novel means of metallizing a surface or the electrodeposition ofmetal thereon, especially in cases where the deposit is to be removedintact. Deposition with a view to removal in this manner may beidentified as electroforming as distinguished from electro-plating.

' The principal object of the invention is to provide a satisfactorymetallized surface for the production of foundry patterns and core boxesby electrolytic means.

Two general applications of electroforming are contemplated; first,where a duplicate or replica of a given object is to be produced, andsecond, where a mold or counterpart is to be made froma given object.The first class is in the nature of patterns and the second in thenature of-core boxes, including also 'molds for the shaping of variousobjects such as rubber products, molded, stone or cement products andimitation wood carvings pressed fromwood pulp composition.

With reference now .to pattern making which is perhaps the mostimportant application of the present process an original pattern in woodor metal is first supplied. A mold of a suitable plastic substance, suchas plaster Paris, is poured over the original pattern and allowed toset. It is then dried and rendered resistant to the electrolytic bath,metallized by means disclosed herein, and finally plated until a coppershell of sufficient thickness is ..forme The shell is reinforced by anymeans such as that disclosed 1 in my co-pending Patent No. 1,792,542 ofFeb. 17, 1931, either before or after removal from the mold. 40 Where itis desired to produce an object in the nature of a core box, such as acore box proper or a mold, it is first necessary to provide an objecthaving the configuration of the product to be molded. The object ormodel is metallized directly, after being ren-- dered resistant to thebath if necessary, plated until the desired thickness of metal isformed, and then separated from the model. Obviously, the deposit may bebacked in any de- 59 sired or suitable manner.

surface are known, it has been found to be decidedly diflicult to selectone that produces an accurate deposit. It is essential in the interestof an accurate reproduction that the metal shall deposit on all parts ofthe surface intended to be metallized and shall not readily separatefrom the metallized surface during-plating. A highly satisfactory meansof metallizing the surface, and which constitutes the subject matter ofthe present invention, consists in applying a solution of a metal to thesurface to be plated and'rubbing over the surface a mixture of graphiteand a metal dust electropositive to the metal in solution. The accuracyof the reproduction obtained on such a surface is indicated by the factthat metal deposited directly on a wood carving shows the grain of thewood, and this grain is effectively reproduced in wood pulp which ismolded by the deposit.

The invention is fully disclosed by way of example in the following(lescri tion and in the accompanying drawing in w ich:

Figure 1 is a plan view of a pattern laid upon a board for the formationof a mold thereover;

Figure 2 is a sectional view showing the mold formed over the pattern;

Figure 3 is a similar section showing the mold removed and metallized;

Figure 4. is a sectional view of an electrolytic'hath showing the moldsuspended there- 1n:

Figure 5 is a sectional view of an object metallized directly;

Figure 6 is a sectional view of said object suspended in a bath for thedepositing of a mold thereon; and

Figure 7 isa sectional view of the deposit backed up as a mold or die.

Reference to these views will now be had by use of like characters whichare employed to designate corresponding parts throughout.

In Figures 1 and 2 is illustrated a pattern 1 which is to be reproducedone or more times. The pattern is laid on a board 2 and surrounded by awall The exposed surfaces of the board and pattern are oiled, as well asthe inner faces of the wall 3, and a I plastic material such as plasterParis is formed by ,meral 4. a mold which may readily be removed frompoured over the pattern to fill the enclosure the wall 3 as ind cated bythe nu- When this material sets it forms the contacting members due tothe fact that the latter have been oiled.

The mold 4 is now dried and rendered resistant to the electrolytic bathby impregnatty 5 which in with wax, although the body may origina 1y beresistant to the bath or may even be impregnated after metallizing.

The mold is obviously formed with a caviis an impression of the pattern1.- The surface of the impression is first treated with a solution of ametal such as an organic solution of silver nitrate with sufficientwater to permit a reaction with a reducing agent subsequently to beapplied.

The organic solvent in this connection is such as to dissolve orpenetrate any remaining wax in the surface and permit the solution toreach the bare surfaces. The surface of the impression is now treatedwith a substance electropositive to the first metal in order to .causeelectrolytic precipitation of the first metal. The electropositivesubstance may be copper dust of about 300 mesh, and in this sprinklingit on the surface of the impression and then brushing off the excess.,eration is repeated until the surface is seen while the precedingsolution is still damp This opto be covered entirely by a metal film,and

three "operations will usually suffice.

used in the solution and as the dust respec tion is such that the Thegraphite appears to act as a lubricant .or'a vehicle in bringing themetal dust into contact with the first reagent at every point throughoutthe surfaces, but whatever the action may be, the metallizing is morethorough than if the metal dust alone were used. It

is also to be understood in this connection that other metals thansilver and copper maybe tively, so long as their electrochemical rela- Idust displaces the metal of the solution. In Figure 3 the numeral 6designates the metallized surface.

The cathode thus'prep'ared is then immersed in an electrolytic tank 7containing a "solution of the metal to be deposited. An

acid copper sulphate bath has been found to yield a very satisfactorydeposit. The metal may be deposited directly out of the solution or froman anode 8l of the metal to be deposited, suspended in the bath.Obviously the cathode and anode are connected respectively to thenegative and positive sides of the circuit.

A shell 9 of deposited metal forms within the cavity 5 on the metallizedsurface 6 and constitutes an accurate dimensional reproduction of theoriginal pattern '1. This shell may then be filled with a suitablematerial and mounted on a plate so that it may be used as a pattern.

Where a mold is to be deposited, a model.

the configuration of the produce of such a mold is first provided. Themodel may be, for example, a wood carving 10 which is mounted on a board11 for convenience in handling, plays no part in the present invention.If the model is not already resistant to the bath it is renderedresistant by preferably soaking in wax at to C. for one half to onehour. The excess wax is wiped off the surface on which deposition is totake place and these surfaces are next metallized to form a conductivefilm 12 in the manner already described.

The model is then immersed in the bath 13 preferably after being mountedon another board 14 to the lower edge of which is attached a weight 15for the purpose of holding the board in a vertical position. This bathis similar to that described in connection with Figure 4. The passage ofcurrent through the bath forms a deposit 16, the interior of whichreproduces all the detail of the plated surface of the model 10. The

or sample having deposit, after reaching a suflicient thickness,

is separated from the model, and after being properly backed andsupported as by means of metal 17 cast over the deposit, may be used asa mold for forming-objects of'the same configuration as the mo innersurface of the deposit is a highly accurate reproduction, in converseform, of the surface which has been metallized. In the case ofdepositing upon wood carvings, for example, it has been found that thedeposit shows even the .grain of the wood, which inturn is reproduced inthe material molded in the deposit.

The deposit 16 is in the nature of a core box and illustrates the methodof forming a core box wherein the molding surfaces consist of depositedmetal. In such case the model 10 would be a body having theconfiguration of the core to be made in the core box. The deposit wouldnaturally be backed and supported for core box use, as shown herein oras disclosed, for example, in my erg-pending Patent No. 1,7 92,542 ofFeb. 17, 1 31.

As a modification of the manner of metallizing, I may first treat theobject with a solvent for the wax or other material on the surface ofthe body, thus bearing the surface forthe application of the conductivecoating. The surface is then thoroughly although the board del 10. The Trubbed with the copper-graphite mixture and finally treated with silvernitrate in a solvent adapted to wet the surface, or in other words,dissolve the remaining surface impregnant not taken up by the firstsolvent.

In either method, however, it will be seen that the surface is firstbared preparatory to receiving the conductive coating formed by thereaction of copper with silver nitrate. In this sense, the solvent ofthe silver nitrate may be described as surface-penetrating.

Although the invention has been developed with the principal object ofmaking patterns and'core boxes by electrolytic reproduction, it is alsouseful in the direct reproduction of other objects by depositing upon amold of such an object and in the formation of molds for various objectsby depositing directly upon such objects.

What I claim is I 1. The method of metallizing an object consisting inbaring the surface of the object, applying thereto a solution of ametal, and brushing. while the solution persists, with a mixture ofgraphite and a metallic dust electropositive to the first named metal.

2. The method of metallizing an object consisting in applying thereto asurface-penetrating solution of a metal, and brushing, While thesolution persists, with a mixture of graphite and a metallic dustelectropositive to the first named metal.

3. The method of metallizing an object consisting in applying thereto asurface-pence trating solution of a metal, and brushing, while thesolution persists, with a mixture of thirty per cent to seventy per centgraphite and seventy per cent to thirty per cent of a metallic dustelectropositive to the first named metal. 7

4. The method of metallizing an object consisting in impregnating thesame with wax, wiping ofl the excess wax from the surface to bemetallized, applying to said surface a wax dissolving and slightlyaqueous solution of a metal, and brushing, while the solution persists,with a mixture of graphite and a metallic dust electropositive to thefirst n amed meta 5. The method of metallizing an object consisting inbaring the surface of the object, applying thereto a slightly aqueoussolution of silver nitrate, and brushing, while the solution persists,with a mixture of graphite and a metallic dust electropositive tosilver.

6. The method of metallizing an object consisting in applying thereto asurface-penetrating and slightly aqueous solution of a reducible silversalt, and brushing, while the solution persists, with a mixture ofgraphite and copper dust.

' 7. The method of metallizing an object consisting in impregnating thesame with Wax, wiping off theexcess wax from the surface to bemetallized, applying to said surface a wax-dissolving and slightlyaqueous solution

